Process and apparatus for the manufacturing of long steel products in a continuous casting plant

ABSTRACT

An apparatus for continuous casting has a withdrawal/straightening unit with pairs of rolls. The spacing distance between two rolls of each pair decrease to create a deformation of a long metal product poured from a mold. A particular deformation is a reduction of the section in one direction, preferably a vertical direction.

The present invention relates to a process and apparatus for themanufacturing of long products in a continuous casting plant.

The term “long products” relates herein to blooms, billets or generallyto all products in their physical form in which they exit from the mouldof a continuous casting machine fed by a steelworks furnace, such as anarc furnace (EAF) or the like.

In order to maximize the yield of a steelworks plant, the use of thecontinuous casting principle, with a direct connection to the millsdownstream, is known.

The creation of this type of plant, however, has considerable problemsdue to the difference in velocity with which the long products leave themould (usually less than 5 m/min) and the velocity at which they must befed to the breaking mills, or the first of the series of rolling stands(usually at least 6 m/min).

If, on the one hand, it is not possible to follow the strategy ofincreasing the casting speed over certain limits (so as not to riskhaving a faulty product), it is not even conceivable, on the other hand,to lower the feeding speed of the mills below certain values (mainly dueto the excessive heating to which they would be subjected and to theexcessive plant expenses for every single laminated product).

Various techniques have been prepared for overcoming these drawbacks: inthe case of thin flat laminates (strips), for example, resort is made tothe presence of two winding stations which, situated upstream of thebreaking mill, create an expansion effect which allows the two differentvelocities to be respected.

Even if this solution is functional, it has the disadvantage, however,of requiring a significant installation cost.

Another solution which is conceptually similar to that described abovebut applied to the field of blooms and billets, is that described in thedocument EP1187686: a main feeding line to the mill exits from thecontinuous casting together with one or more parallel auxiliary linesfrom which the rough products of the feeding are transferred to the mainline to be processed; in short, these auxiliary lines again merely actas a “buffer” for the feeding of the mill.

A first drawback of this solution relates to the fact that in order toeffect the passage from an auxiliary line to the main line, appropriatetransversal transfer systems must be set up.

Furthermore, the control of the transfer rates of the rough products inthe feeding (different for the main line and the auxiliary line) must beparticularly precise in order to allow the regular continuous feeding ofthe mill.

There are also known processings, such as that described in the patentEP0603330 or in the patent application US2009/0056906, which are capableof slightly increasing the velocity of the elongated product from whenit leaves the mould to when it enters the withdrawal/straightening unit(often indicated with the acronym W.S.U).

It should be immediately noted that the increase in the rate of therough products is a necessary consequence of the process which isdescribed herein, but not the main objective of this process, which hasbeen conceived for other purposes.

Before entering into the details of the description of these solutions,it should be pointed out that in these types of plant, the product Pleaves the ingot mould vertically and is then deformed along a sectionof circumference until it acquires a horizontal position and straighttrajectory, in order to limit the vertical encumbrances of the plant.

As a result, in all of these plants, the trajectory followed by theproduct P comprises a first portion, immediately downstream of the mouldsection, which develops according to a circular section with an openingof about 90° (from vertical to horizontal) and a second portion whichdevelops horizontally: the joining section of the two trajectories(curved and straight line) is indicated with the term “transition area”.

The W.S.U. (Withdrawal Straightening Unit) is typically positioned incorrespondence with this area, which straightens the product P from acurved form to a straight form and allows the withdrawal speed to becontrolled.

The W.S.U. obviously acts with its rolls in the sections of trajectorysituated immediately upstream and downstream of the transition area.

In order to understand the processing described in the documentEP0603330, reference should be made to FIG. 1: this shows the terminalpart of the mould L of a continuous casting from which a product Pexits.

According to the teachings of EP0603330, the plant must be modified anddimensioned so that the “metallurgical length” of the product P istotally included within the curved section (from the ingot mould to theW.S.U. rolls), i.e. upstream of the transition area, shown in FIG. 1with the reference ZT.

“Metallurgical length” indicates the portion of product P in which thereis a central nucleus, not yet completely solidified (solid grains insuspension coexist in the nucleus, in a liquid matrix).

Also in this case, the W.S.U. is not a traditional unit, but isspecifically produced so that it acts only on the straight portion,downstream of the transition area ZT: this special W.S.U. in factcomprises a series of rolls, all positioned downstream of the transitionarea ZT and having rotational axes parallel to each other andsubstantially positioned at the same distance from the product P.

The product P, immediately downstream of the mould, passes through therolling stands R, which are structured so as to generate a deformationof the product which creates a sectional variation obtained bymaintaining the perimeter of the product P constant.

This deformation is often defined in the technical field as “soft corereduction” and has the primary objective of improving the quality of thefinished product.

Under certain conditions, the sectional variation of the product P couldobviously be useful for increasing the advance speed of the product.

By following the teachings provided by the patent EP0603330, however,this increase in rate is too limited to allow a direct feeding to themill RM without using expedients described above (i.e. the “buffer”solutions).

Furthermore, in addition to not being able to be used for thesepurposes, the solution illustrated in EP0603330 has various drawbacks.

First of all, the plant set-up is extremely expensive, as the rollingstands R must be produced with “nipper” shells suitable for being openedand closed to allow the passage of the so-called “head of the dummy bar”in the initial start-up phase of the plant, which has a fixed section,equal to that of the outlet mouth of the mould.

In order to allow the passage of the head of the dummy bar, the rollingstands R must not have a conical passage section, otherwise the head(with a fixed dimension) would not be able to pass.

This solution, moreover, is quite complex to effect and is mainlysuitable for products P having small dimensions: maintaining themetallurgic length within the curved section, in fact, alternativelyrequires either an extremely reduced advance speed (which consequentlydoes not help to reach the feeding rate of the mills) or an extremelywide curvature radius (with negative consequences in terms of verticalencumbrance of the plant with relative costs).

Yet another drawback is linked to the fact that the W.S.U. must bespecifically designed and produced for this plant.

The disclosure of US2009/0056906 is based on the basic teachings ofEP0603330 discussed so far, and even if there is apparently an assemblyin line with the lamination stations, the latter (for the reasonsdiscussed above) are presumably fed at a low speed, with the drawbackspresented above.

From what is specified above, it appears evident that it is necessary toavail of a process and apparatus for the manufacturing of long productsin a continuous casting plant, wherein the mills can be fed in a simpleand inexpensive manner.

In particular, an objective of the present invention is to solve theabove-mentioned drawbacks by providing a process and apparatus for themanufacturing of products in a continuous casting plant in which it ispossible to obtain an acceleration of the product downstream of theingot mould so that the advance rate of the product can be increasedfrom the initial casting rate to the feeding rate of the mills, withouthaving to apply costly modifications to the known plants and maintainingrelatively limited encumbrances.

These objectives are achieved according to a first aspect of theinvention by a process for the manufacturing of a long metallic productin a continuous casting plant, wherein said product follows a trajectorycomprising a curvilinear section and a straight section. The processcomprises at least a first and a second deformation phase, each of saidphases comprising a contemporaneous deformation of the perimeter and ofthe transversal section of said product, the first deformation phasebeing effected in said curvilinear section and the second deformationphase being effected in said straight section, the first and the seconddeformation phase being effected in an area where liquid metal is stillpresent in the product and at a location where each deformation provokesan increase in the speed of the product.

The process according to the invention may also comprise the followingsteps:

-   -   a further deformation of said perimeter and said transversal        section of said product occurs in a transition area located        between the first and the second deformation,    -   said deformation phases create a deformation of the section of        said product in one direction, preferably a vertical direction,    -   there are further deformation phases along said deformation line        (LD)    -   said deformation phases create a deformation of the section of        said product in two directions perpendicular to each other,        preferably in an alternating horizontal and vertical direction.

The process according to the invention may also comprise the followingsteps:

-   -   a—casting a long metallic product with a square section, the        product advancing along a trajectory comprising a curvilinear        section and a straight section, the extremity of a metallurgical        line of said product being upstream and downstream of a        transition area located between said curvilinear section and        said straight section;    -   b—deforming said product upstream of said transition area to        reduce said section in a first direction, preferably vertical,        so as to obtain a rectangular section;    -   c—deforming said product in said transition area to further        reduce said section in said first direction, thus obtaining a        rectangular section;    -   d—further deforming said product downstream of said transition        area to further reducing said section in said first direction,        thus obtaining a rectangular section;

The process according to the invention may also comprise the followingsteps:

-   -   a1—casting a long metallic product with a mould, the product        advancing along a trajectory comprising a first curvilinear        section and a second straight section, the extremities of a        metallurgical line of said product being upstream and downstream        of a transition area located between said curvilinear section        and said straight section;    -   b1—deforming of said product upstream of said transition area to        reduce said section in a first direction, preferably vertical,        so as to obtain a rectangular section;    -   c1—deforming said product upstream of said transition area to        reduce said section in a second direction perpendicular to said        first direction, preferably horizontal, so as to obtain a square        section;    -   d1—deforming said product in said transition area to further        reduce said section in said first direction, thus obtaining a        rectangular section;    -   e1—deforming of said product in said transition area to further        reduce said section in said second direction;    -   f1—deforming said product downstream of said transition area to        further reduce said section in said first direction, thus        obtaining a rectangular section;    -   g1—deforming said product downstream of said transition area, to        further reduce said section in said second direction.

In one embodiment the reduction of said section in said first or saidsecond direction which is obtained as a whole between the sectionupstream of the first deformation and that downstream of a lastdeformation ranges from 14% to 16.8%, and is preferably equal to 15.4%of the initial dimension.

In one embodiment the advance speed of said product downstream of saidingot mould is equal to about 5 m/min.

In one embodiment said deformations are created in awithdrawal/straightening unit of said product.

According to a second aspect, the invention also relates to an apparatusfor manufacturing a metallic long product which effects the abovementioned process.

The apparatus may comprise:

-   -   means for guiding the product along a trajectory comprising a        curvilinear section and a straight section;    -   a withdrawal/straightening unit comprising a plurality of pairs        of rolls wherein at least a first pair of rolls is located in        said curvilinear section and at least a second pair of rolls is        located in the straight section, the first an the second pair of        rolls being further located in an area where liquid metal is        still present in the product and at a location where the rolls        provoke an increase in the speed of the product.

In one embodiment the distances between two consecutive rolls of twoconsecutive pairs decrease to create a deformation of a long metallicproduct poured from a mould, in particular a reduction of the section inone direction, preferably a vertical direction.

The withdrawal/straightening unit may comprises alternating pairs ofrolls having perpendicular rotation axes between rolls of adjacentpairs, in particular alternating horizontal and vertical axes, whereinthe distances between two rolls of each pair decrease to create adeformation of a long metallic product poured from a mould, inparticular a reduction of the section on two directions, preferably avertical direction and a horizontal direction.

In short, the Applicant has observed that the above mentioned objectivecan be achieved by reducing the section and perimeter of the product, byacting in both the area prior to and subsequent to the transition areafrom the curved form to the linear form of the product, said reductionsin the section and perimeter being effected under conditions of theproduct having a nucleus not completely solidified and at a locationwhere the product can be significantly accelerated.

In this case, the section and perimeter are modified in the developmentof the metallurgical length, which extends beyond the transition area ofthe product from curvilinear to rectilinear.

In this way, without the casting speed exceeding 5 m/min, it is possibleto increase the advance speed of the product to the feeding speed of themills, i.e. 6 m/min.

The structural and functional characteristics of the invention and itsadvantages with respect to the known art, can be clearly understood fromthe following description, referring to the enclosed drawings, whichshow a possible embodiment of the invention.

In the drawings:

FIG. 1 shows a solution of the known art;

FIG. 2 shows a scheme of a first embodiment of the present invention;

FIG. 3 shows a scheme of a second embodiment of the present invention;

FIG. 4 shows a plurality of transversal sections of a product duringdifferent operating phases of the process according to the presentinvention.

With reference to FIG. 2, this shows a scheme relating to the processand apparatus according to a first embodiment of the present invention.

In general the process for manufacturing an elongated metal product 1 ina continuous casting plant according to the present invention, envisagesthat the product 1 follow a trajectory comprising a curvilinear sectionand a straight section and that it comprises at least a first and asecond deformation phase, each of said phases including acontemporaneous deformation of the perimeter and transversal section ofsaid product 1.

According to the teachings provided herein, the first and second phaseare respectively effected, one in the curvilinear section and the otherin the straight section.

The first and second deformation phases respectively define twoextremities of a deformation line indicated by LD and located on abarycentric axis of the product 1.

This deformation line LD is included within a metallurgical line (alsocalled metallurgical length) LM measured on the same barycentric axis ofsaid product 1 and delimitated by a first extreme point in whichoverheated liquid metal is present in the product 1, and a secondextreme point in which said product 1 is completely solidified; thisaspect will be dealt with further on.

In a first basic version, the process envisages the deformation of thesection and perimeter of the product, by acting in a single direction,preferably a vertical direction.

A more developed variant of the process and relative apparatus envisagesthat the deformation be effected by acting in two perpendiculardirections, horizontal and vertical.

With respect to FIG. 2, reference 1 indicates the elongated productwhich vertically leaves the ingot mould 2, whereas reference 10indicates the apparatus as a whole.

The product 1 is preferably steel in the form of a billet or bloom orsimilar sections.

Downstream of the ingot mould 2, the product 1 is guided by guidingrolls 3 (dotted line) as far as the straightening/withdrawal unit(W.S.U.) indicated as a whole by reference 4.

The W.S.U. includes at least three pairs of rolls 4A, 4B, 4C, situated,with reference to the transition area ZT (point or region in which theproduct 1 passes from a curved to a flat configuration) upstream (rolls4A) of the area ZT, in correspondence with the area ZT (rolls 4B) anddownstream of the area ZT (rolls 4C).

The rolls 4A, 4B and 4C all have a horizontal axis and at least oneroll, preferably one for each pair, is motorized.

More specifically, for the rolls of the upstream pair 4A and incorrespondence 4B with the area ZT, it can be observed that the rotationaxes of the rolls of each pair 4A, 4B lie along the same radiusconnected to a single centre CM, i.e. the so-called “machine centre”,which is the centre of the circumference with subtends the arc ofmagnitude 90° on which the curved trajectory of the product 1 isdeveloped, downstream of the ingot mould and upstream of the transitionarea ZT.

The distance between the first pair of rolls 4A and the second pair ofrolls 4B is greater than the distance between the second pair of rolls4B and the third pair of rolls 4C, thus creating a deformation of theproduct 1, in particular a reduction in the section in one direction, inparticular vertical.

More specifically, the decrease in the vertical dimension which isobtained as a whole between the section upstream of the first pair ofrolls 4A and downstream of the third pair of rolls 4C ranges from 14% to16.8%, preferably equal to 15.4%.

According to the conservation of mass principle, under these conditions,the speed downstream of the third pair of rolls 4C is increased by avalue equal to about 18.7%.

It can therefore be said that the process effected comprises thefollowing steps:

a—preparing a metallic product 1 with a square section, preferably witha side of 130 mm, poured from a mould 2 and suitable for advancing withan advance speed preferably equal to 5 m/min along a trajectorycomprising a first curvilinear section and a second straight section,the extremities of a metallurgical line LM of said product 1 beingupstream and downstream of a transition area ZT between said curvilinearsection and said straight section;

b—deforming said product 1 upstream of said transition area ZT to reducesaid section in a first direction, preferably vertical, so as to obtaina rectangular section preferably having sides of 130 mm and 122 mm;

c—deforming of said product 1 in said transition area ZT to furtherreduce said section in said first direaction, thus obtaining arectangular section preferably having sides of 130 mm and 116 mm;

d—further deforming said product 1 downstream of said transition areaZT, to further reduce said section in said first direction, thusobtaining a rectangular section preferably having sides of 130 mm and110 mm.

Under operative conditions, the best results are obtained in fact whenthe product 1, downstream of the ingot mould 2, has a substantiallysquare section, with a side of 130 mm and an advance speed equal toabout 5 m/min.

Under these conditions, the following steps are effected:

-   -   a first deformation realized by the first pair of rolls 4A so as        to allow the product 1 to acquire a substantially rectangular        section with sides of 130 mm and 122 mm.    -   a second deformation realized by the second pair of rolls 4B so        as to allow the product 1 to acquire a substantially rectangular        section with sides of 130 mm and 116 mm.    -   a third deformation realized by the third pair of rolls 4C so as        to allow the product 1 to acquire a substantially rectangular        section with sides of 130 mm and 110 mm.

It should be noted that the section to which reference is made above isindicated as “substantially” rectangular as, in reality, it has roundededges which normally derive from the deformation of the product 1 in adimension (vertical) and under these operative conditions.

Under these conditions, the speed downstream of the third pair of rolls4C is equal to about 6 m/min, and therefore optimum for sending theproduct 1 directly to a mill L.

Optionally, before the mills L, the product 1 can be preheated in aninduction furnace or similar.

It is fundamental to remember that, for the purposes of the presentinvention, the semi-solid core 11 of the product 1 extends in thedeformation area between the first 4A and third 4C pair of rolls.

It would be convenient, at this point, to briefly explain how thesolidification of the product 1 takes place downstream of the mould 2.

In the very first area downstream of the mould 2, the product 1 has arelatively reduced “skin thickness” (i.e. a thickness of the solidperimetric wall 12).

The central nucleus, or core 11, of the product 1, extends significantlyin this area and approximately occupies a surface higher than 80% of thetransversal section of the product 1.

The temperature of the nucleus 11 is obviously higher than that of theperimetric wall 12, so that both the liquid phase and metal grainsalready solidified co-exist in said nucleus 11.

Due to the progressive cooling, along the trajectory followed by theproduct 1, the skin thickness 12 tends to increase and the section ofthe nucleus 11 to progressively decrease.

According to the teachings provided herein, it is therefore necessaryfor the “metallurgical line” LM (referring to the length of the portionof product 1 measured on the barycentric axis of the product 1 and inwhich there is a central nucleus not yet completely solidified, in whichsolid grains and not overheated liquid metal co-exist, LM being measuredfrom the exit of the mould 2), to extend beyond the last pair of rolls4C of the W.S.U. machine 4.

The deformation line LD must therefore be included within themetallurgical length LM.

In short, the product 1 must reach the transition area ZT still providedwith a semi-liquid core which continues to be present at least as far asthe last roll 4C of the W.S.U. 4, as schematically illustrated in FIG. 4enclosed. Furthermore the rolls, and in particular the first pair ofrolls 4A, are located at a position where the solidified skin thickness12 is important enough so that the deformation realized by the rollsalso provokes an increase of the speed of the product in the advancingdirection of the product. In other words the rolls should not be locatedtoo close to the mould 2 where the product is still too liquid and wherethe deformation would not provoke sufficient acceleration of theproduct.

This is dimensionally obtained, in a preferred solution, respectingthese conditions:

Dimensions of the sides Reduction L1, L2 of the transversal phasessection of the product 1 Advance speed V Initial measurement L1 = 130 mm  5 m/min L2 = 130 mm Final measurement L1 = 130 mm 5.9 m/min L2 = 110mm

It should be immediately noted that variants can be applied in whichthere is a reduction in only two steps, for example only incorrespondence with the first rolls 4A and third rolls 4C, all includedin the scope of the present invention.

A further variant is shown in FIG. 3, in which the same parts areindicated with the same reference numbers and consequently no furtherreference will be made thereto.

In this case, the apparatus differs from the apparatus previouslydescribed in that the W.S.U. 45 comprises both the pairs of rolls 4A,4B, 4C described above and also a plurality (for example three) of pairsof rolls 5A, 5B, 5C having a rotation axis perpendicular to that of thepairs of rolls 4A, 4B, 4C.

The pairs 4A, 4B, 4C for example, have a horizontal axis, whereas thepairs 5A, 5B, 5C have a vertical axis.

In particular, the W.S.U. machine 45 in this case comprises both seriesof rolls, the pairs with a horizontal axis 4A, 4B, 4C, and also thosewith a vertical axis 5A, 5B, 5C alternating, so that a pair of rollswith a horizontal axis is followed by a pair with a vertical axis andvice versa.

The first pair of rolls 4A of the W.S.U. machine 45 which the product 1encounters when leaving the mould 2 is preferably a pair of rolls with ahorizontal axis.

In this case, the pairs of rolls 4A, 4B, 4C, 5A, 5B, 5C are arranged anddimensioned so as to generate a deformation of the product 1 in twodirections perpendicular to each other, preferably horizontal andvertical.

The arrangement of the pairs of rolls 4A, 4B, 4C, 5A, 5B, 5C is suchthat a deformation in a vertical direction is followed by a deformationin a horizontal direction and vice versa.

The advantages in this case are substantially analogous to those offeredwith the apparatus 1 and consequently no further mention will be made tothis, except for pointing out that the deformation in two directionsallows a much higher final speed (downstream of the rolls 5C) of theproduct 1 to be obtained.

Also in this case, the “metallurgical line” LM can extend beyond thelast pair of rolls 5C of the W.S.U. machine 45 and the deformationlength LD is included within the metallurgical line LM.

This is dimensionally obtained, in a preferred solution, respecting thefollowing conditions:

Dimensions of the sides Reduction L1, L2 of the transversal Advancephases section of the product 1 speed V Initial measurement L1 = 130 mm5 m/min L2 = 130 mm Final measurement L1 = 110 mm 7 m/min L2 = 110 mm

It can therefore be said that in this variant, the process comprises thefollowing steps:

a1—preparing a metallic product 1 with a square section, preferably witha side of 130 mm, poured from a mould 2 and suitable for advancing withan advance speed preferably equal to 5 m/min along a trajectorycomprising a first curvilinear section and a second straight section,the extremities of a metallurgical line LM of said product 1 beingupstream and downstream of a transition area ZT between said curvilinearsection and said straight section;

b1—deforming said product 1 upstream of said transition area ZT toreduce said section in a first direction, preferably vertical, so as toobtain a rectangular section preferably having sides of 130 mm and 122mm;

c1—further deforming said product 1 upstream of said transition area ZTto reduce said section in a second direction perpendicular to said firstdirection, preferably horizontal, so as to obtain a square sectionpreferably having sides of 122 mm;

d1—further deforming said product 1 in said transition area ZT tofurther reduce said section in said first direction, thus obtaining arectangular section preferably having sides of 122 mm and 116 mm;

e1—further deforming said product 1 in said transition area ZT tofurther reduce said section in said sec- and direction, thus obtaining asquare section preferably having sides of 116 mm;

f1—further deforming said product 1 downstream of said transition areaZT, to further reduce said section in said first direction, thusobtaining a rectangular section preferably having sides of 116 mm and110 mm;

g1—further deforming said product 1 downstream of said transition areaZT, to further reduce said section in said second direction, thusobtaining a square section preferably having sides of 110 mm.

A further advantage obtained with the present invention is that theW.S.U. machine 4 can be a machine, in which there is the expedient ofpositioning the pairs of rolls 4A, 4B, 4C at suitable distances in orderto effect the method described above.

Alternatively, a W.S.U. machine can be modified by adding two, three ormore pairs of rolls 5A, 5B, 5C with a horizontal axis to cause areduction in the section of the product 1 in more than one direction.

Numerous modifications to what has been described so far can obviouslybe applied, for example the reduction percentages can vary from one pairof rolls to the subsequent pair, or the sections can be different fromsquare or rectangular.

The objectives indicated in the preamble of the description havetherefore been achieved.

The scope of the invention is defined by the following claims.

1-14. (canceled)
 15. A process for manufacturing an elongated metallicproduct in a continuous casting plant, the process comprising:conducting the product to follow along a trajectory with a curvilinearsection and a straight section; deforming the product in a plurality ofdeformation phases including at least a first deformation phase and asecond deformation phase; each of said deformation phases including acontemporaneous deformation of a perimeter and a transversal section ofthe product; implementing the first deformation phase in the curvilinearsection and implementing the second deformation phase in the straightsection, effecting the first and second deformation phases in an areawhere liquid metal is still present in the product, and at a locationwhere each deformation of the product provokes an increase of a speed ofthe product.
 16. The process according to claim 15, which compriseseffecting a further deformation of the perimeter and the transversalsection of the product in a transition area located between the firstdeformation and the second deformation.
 17. The process according toclaim 15, wherein the deformation phases cause a deformation of therespective section of the product in one direction.
 18. The processaccording to claim 17, wherein the one direction is a verticaldirection.
 19. The process according to claim 15, which comprisesimplementing further deformation phases along the deformation line. 20.The process according to claim 15, which comprises configuring thedeformation phases to create a deformation of the respective section ofthe product in two mutually perpendicular directions.
 21. The processaccording to claim 20, wherein the two mutually perpendicular directionsare alternating horizontal and vertical directions.
 22. The processaccording to claim 15, comprising the following steps: a) casting anelongated metal product with a square section, and advancing the productalong a trajectory including a curvilinear section and a straightsection, wherein an extremity of a metallurgical line of the product isupstream and downstream of a transition area located between thecurvilinear section and the straight section; b) deforming the productupstream of the transition area to reduce the section in a firstdirection, so as to obtain a rectangular section; c) deforming theproduct in the transition area to further reduce the section in thefirst direction, thus obtaining a rectangular section; d) furtherdeforming the product downstream of the transition area to furtherreduce the section in the first direction, thus obtaining a rectangularsection.
 23. The process according to claim 22, which comprises thefollowing steps: a1) casting a long metallic product with a mold, theproduct advancing along a trajectory including a first curvilinearsection and a second straight section, the extremities of ametallurgical line of the product are upstream and downstream of atransition area located between the curvilinear section and the straightsection; b1) deforming the product upstream of said transition area toreduce the section in a first direction so as to obtain a rectangularsection; c1) deforming the product upstream of said transition area toreduce the section in a second direction perpendicular to the firstdirection, so as to obtain a square section; d1) deforming the productin the transition area to further reduce the section in the firstdirection, thus obtaining a rectangular section; e1) deforming of theproduct in the transition area to further reduce the section in thesecond direction; f1) deforming the product downstream of the transitionarea to further reduce the section in the first direction, thusobtaining a rectangular section; and g1) deforming the productdownstream of the transition area, to further reduce the section in thesecond direction.
 24. The process according to claim 22, wherein areduction of the section in the first direction or in the seconddirection that is obtained as a whole between the section upstream ofthe first deformation and the section downstream of a last deformationranges from 14% to 16.8% relative to an initial dimension.
 25. Theprocess according to claim 24, wherein the reduction obtained as a wholeis equal to 15.4% of the initial dimension.
 26. The process according toclaim 15, which comprises advancing the product with an advance speeddownstream of an ingot mold amounting to approximately 5 m/min.
 27. Theprocess according to claim 15, which comprises implementing thedeformations in a withdrawal/straightening unit of the product.
 28. Anapparatus for manufacturing an elongated metal product, comprisingdevices configured for carrying out the process according to claim 15.29. The apparatus according to claim 28, which comprises: means forguiding the product along a trajectory including a curvilinear sectionand a straight section; a withdrawal/straightening unit containing aplurality of pairs of rolls, including at least a first pair of rolls inthe curvilinear section and a second pair of rolls in the straightsection; said first pair of rolls and said second pair of rolls beingdisposed in an area where liquid metal is still present in the productand at a location where said rolls provoke an increase in a speed of theproduct.
 30. The apparatus according to claim 29, wherein said rolls ofsaid pairs of rolls are disposed at a spacing distance from one another,and said spacing distances between two respective rolls of twoconsecutive pairs decrease to create a deformation of an elongatedmetallic product poured from a mold.
 31. The apparatus according toclaim 30, wherein said rolls of said pairs of rolls are disposed tocause a reduction of a section of the product in one direction.
 32. Theapparatus according to claim 31, wherein the one direction is thevertical direction.
 33. The apparatus according to claim 28, whereinsaid withdrawal/straightening unit comprises alternating pairs of rollshaving mutually perpendicular rotation axes between rolls of adjacentpairs, wherein spacing distances between two rolls of each pair decreaseto create a deformation of an elongated metallic product poured from amold.
 34. The apparatus according to claim 33, wherein saidperpendicular rotation axes are alternating horizontal and verticalaxes.
 35. The apparatus according to claim 33, wherein said rolls aredisposed to implement a reduction of the section on two directions,namely, a vertical direction and a horizontal direction.